netdev - Re: [PATCH v10 12/12] bpf: add sample for xdp forwarding and rewrite

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Date:	Wed, 27 Jul 2016 20:25:48 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Brenden Blanco <bblanco@...mgrid.com>, davem@...emloft.net,
	netdev@...r.kernel.org, Jamal Hadi Salim <jhs@...atatu.com>,
	Saeed Mahameed <saeedm@....mellanox.co.il>,
	Martin KaFai Lau <kafai@...com>, Ari Saha <as754m@....com>,
	Or Gerlitz <gerlitz.or@...il.com>, john.fastabend@...il.com,
	hannes@...essinduktion.org, Thomas Graf <tgraf@...g.ch>,
	Tom Herbert <tom@...bertland.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Tariq Toukan <ttoukan.linux@...il.com>, brouer@...hat.com,
	Rana Shahout <ranas@...lanox.com>
Subject: Re: [PATCH v10 12/12] bpf: add sample for xdp forwarding and
 rewrite

On Tue, 19 Jul 2016 15:05:37 -0700
Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> On Tue, Jul 19, 2016 at 12:16:57PM -0700, Brenden Blanco wrote:
> > Add a sample that rewrites and forwards packets out on the same
> > interface. Observed single core forwarding performance of ~10Mpps.
> > 
> > Since the mlx4 driver under test recycles every single packet page, the
> > perf output shows almost exclusively just the ring management and bpf
> > program work. Slowdowns are likely occurring due to cache misses.  
> 
> long term we need to resurrect your prefetch patch. sux to leave
> so much performance on the table.

I will do some (more) attempts at getting prefetching working, also in
a way that benefit the normal stack (when I'm back from vacation, and
when net-next opens again).

I think Rana is also looking into this for the mlx5 driver (based on
some patches I send to her).

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer